Body oblong and flattened. Antenna 1 well developed, with a multiarticulate flagellum; antenna 2 long, with a scale on the outside of the peduncular article 3. Eyes dorsal. Mandible normal, with a strong, truncated molar process. Anterior pereion segments with smooth sides; coxal plates bilobed. Pleon of one small, inconspicuous segment, others all fused with the telson to form a large, shield-shaped pleotelson. Postero-lateral borders of pleotelson serrated. Uropods with a peduncle, shorter than the pleotelson. Adult male with the preoperculum flat and expanded at the tip with acute corners. Coxal plates visible from above on most pereion segments.
Male body length 6 mm; female 4 mm.
Among sponges, coelenterates, bryozoans, tunicates, Laminaria holdfasts etc., usually well below tidemarks.
Records are from southwest Ireland, North Sea, Norway, Skagerak and Kattegat.